In the art directed to the disposable syringes, it is known to provide a collapsible container for expressing medicines and the like through a needle, into humans or animals, for example. In my earlier U.S. Pat. No. 3,192,925, a previous development of mine sets forth many of the parameters and utilities for devices of this type. However, in some instances it is desired to be able to express a predetermined quantity of medicine, inoculant or the like with precise measurement that can only be obtained by discharging all of the medicine, serum, or other liquid from the flexible container.
In the device of my above-mentioned previous invention, at the discharge end of the tubular container, as the container is being flattened or squeezed into a flattened condition such as will facilitate the discharge, that portion of the container that is immediately adjacent the needle holder or needle carrier, but still inside the container, may not be flattened by compressing the opposite sidewalls of the tubular container together, due to the presence of the needle carrier. Thus, a zone of triangular cross-section often remains in the usual embodiment of my previous invention, whereby not quite all of the substance in the container is discharged therefrom. The problem in complete discharge of fluid from a container is similar to that that is experienced in attempting to discharge the last possible amount of toothpaste from a conventional toothpaste tube, such that the neck of the toothpaste tube, being generally non-flexible relative to the body of the tube, prohibits the complete discharge.
Also, in other syringe types of devices, it is not readily apparent when complete discharge from a flexible tube or container has been effected. The physician, nurse, or the like must be extremely careful to flatten the container completely, or a given injection may introduce an expression of less than the full or complete quantity of liquid in the container. In some instances, this can be highly critical, for example, in injecting insulin into the body of a diabetic, wherein a precise amount of insulin must be carefully controlled. If a given injection is "short" relative to the desired injection, serious consequences can result.